Method of manufacturing filaments for electric lamps.



by pressure.

UNITED em s; PATENT OFFICE.

WERNER VON BOLTON, OF CHARLOTTENBURG, GERMANY, ASSIGNOR TO SIEMENS & HALSKE, A. 6., OF BERLIN GERMANY, A CORPORATION OF GERMANY.

IMETHOD OF MANUFACTURING FILAMENTS FOR ELECTRIC LAMPS.

To all whom it may concern):

Be it'known that I, WERNER VON BOLTON,

a subject of the Czar of Russia, and residing at Am Liitzow 10, Charlottenburg, near Berlin, Germany, have-invented Improvements in Methods of Manufacturing Filaments for Electric Lamps, of which the following is a specification.

The present invention has for its object an improved method of manufacturing filaments of highly refractory metals for electric incandescent lamps.

In order to be able to bring metals, which in themselves alone can only be molded with difiiculty, as, for example, tantalum, tungsten, molybdenum, into the form of filaments for electric incandescent lamps, in accordance with the present invention the concerned metal is embedded in a state of fine division in another metal, as, for example, thorium, gold, copper, aluminium, and particularly nickel, in such a manner that each of the finest particles of the concerned metal is inclosed by a casing of the other metal. This metallic mass which is thus obtained is then wrought into the form of filaments mechanically by rolling or drawing, or under certain circumstances by pressing, squirting or the like, whereuponin case of need the inclosing metal can be removed by mechanical or chemical means or by vaporization.

One metallic powder can be embedded in another ductile metal in the most different ways, as, for example, by the metallic powder being put into a molten mass of the other concerned metal and distributed uniformly in the latter, ,or by a powder of the one metal being intimately mixed with a powder of the other metal and afterward united During the application of.-pres sure to the mixed powder, the ductile metal yields and unites into small plates which cohere and form a covering or casing for the non-duetilemetal. The union can also be effected in the latter case by the mixture of the metallic powders being subsequently heated in such a manner that the ductile metal, which is supposed to be less refractory, is converted into one cohesive mass by its parts being welded or sintered together, or by its parts being united in a melted Specification of Letters Patent. Application filed October 22, 1907. Serial No. 398,675.

lamps consist ng in mixmg I Patented July 13,1909.

state, which cohesive mass envelops the particles of the metallic powder of the highly rofractorymetal.

When it is desired toremove the enveloping metal, this can be done for example, if the enveloping metal is not employed in too great excess, by passing through it an electric current by which the filament is heated, so that the enveloping metal is volatilized. The metallic particles which remain behind then sinter together into one filament. If another metal is employed as the enveloping metal which itself possessesa very high melting point, this can remain in the finished filaments. Thorium metal, for example, is such an exceedingly easily ductile metal having a very high melting point and one which can be workedup mechanically in this manner. 7

What I claim as my invention and desire to secure by Letters Patent is i 1. A method of manufacturing filaments of highly refractory metals for electric lamps consisting in surrounding each particle of the comminuted concerned metals with a casing of another ductile metal and f0rming a cohesive mass of the metals and in forming the mass into filaments.

2. A method of manufacturing filaments of highly refractory metals for electric lamps consisting in comminuting another ductile metal, in mixing the comminuted uniting the same into a cohesive mass in such a manner that each particle of the highly refractory metals is surrounded with a casing of the ductile met-a1, and in forming the mass into filaments. H

3. A method of manufacturing filaments of highly refractory metals for electric lamps consisting in mixing the comminuted highly refractory metals and comminuted ductile metal intimately together and electrically heating the same into a cohesive mass in such a manner that-each particle of the highly refractory metal is surrounded with. a casing of theductile metal, and in drawing the mass into filaments.

at. A' method of manufacturing filaments of highly refractory metals for electric the comminuted concerned metals intimately together and highly refractory metals and comminuted In testimony whereof I have signed my thorium metal intimately together and unitname to this specification in the presence of ing the same into a cohesive mass in such a two Witnesses.

manner that each particle of the highly re- WERNER VON BOLTON. 5 fractory metals is surrounded with a casing Witnesses: of thorium, and in forming the mass into HENRY HAsPER,

filaments. I WOLDEMAR HAUPT. 

